1. Field of the Invention
The present invention relates to methods of improving the health of hair and the scalp. More particularly, this invention relates to methods for reducing hair shedding, methods for increasing hair diameter, and methods for maintaining hair in the anagen phase for a prolonged period of time.
2. Description of Prior Art
Dandruff ("pityriasis capitis sicca") and seborrheic dermatitis ("pityriasis capitis oleosa") are two related clinical manifestations of one common dermatological disorder that involves the scalp as well as other areas of the body having a high density of sebaceous glands. While dandruff is primarily a scaling condition, it is often also associated with some inflammation. See e.g. Dawber, P., "The Scaly and Itchy Scalp," Hair and Scalp Disorders 191-227 (1995). Typically dandruff is expressed on the scalp, but other areas of the body that are predisposed to seborrheic dermatitis also often show mild scaling without obvious signs of inflammation. In seborrheic dermatitis, the inflammatory counterpart of the same disorder, erythema is always present, and the inflammatory infiltrate is more pronounced. See e.g. Ford, G. P., et al., 111 Br. J. Dermatol 603-07 (1984)("Ford").
Those of skill in the art have come to the consensus that both dandruff and seborrheic dermatitis are two aspects of the same disease. See Ford; Sabouraud, R., "Maladies Due Cuir Chevelu II," Les Maladies Desquamatives, 207-327 (1904); and Van Vloten, W., et al., "Eczeem," 8 Dermatologie and Venereologie 90-109 (1996). It is well known that individuals who have dandruff will, if the condition is not treated, often develop the more inflammatory aspect--seborrheic dermatitis, while those having seborrheic dermatitis might show scaling only during the periods of less pronounced inflammation. Although those skilled in the art generally agree that the lipophylic yeast, Pityrosporum ovale ("P. ovale"), is a key contributor in the pathogenesis of seborrheic dermatitis and dandruff, it is likewise accepted that both conditions should not be regarded as an infection. Rather, it is the yeast's overcolonization of the scalp and other body areas having a high density of sebaceous glands that causes a very mild inflammatory reaction, i.e. dandruff, or a moderate inflammatory reaction, i.e. seborrheic dermatitis, redness, as well as an accelerated turnover of the epidermis. See Ford and Arese, J., et al., "Effect of Ketoconazole Medicated Shampoos on Squamometry and Malassezia Ovalis Load in Pityriasis Capitis," 58 Cutis 235-37 (1996).
Typical primary symptoms of dandruff and seborrheic dermatitis include scaling, redness, and itching; however, several other clinical manifestations such as seborrhea (oiliness), telogen effluvium (shedding), thin shaft diameter, androgenic alopecia, and reduction in percent anagen hairs have also been reported in conjunction with this disorder. See Shuster, S., "Psoriatic Alopecia," 87 Br. J. Dermatol. 74-77 (1972); Rushton, D. H., et al., "Natural Progression of Male Pattern Baldness in Young Men," 16 Clin. Exp. Dermatol. 188-192 (1991); Bergfeld, F. W., "Hair Disorders" Dermatology 1541-1560 (1992); and Pierard-Franchimont, C., et al., "Approche Physiopathologique de la Seborrhee Du Cuir Chevelu," 115 Ann. Dermatol. Venereol. 451-53 (1988).
Various methods have been employed to stimulate the growth of hair and/or increase its diameter; however, these methods are not without their shortcomings. One known method employs the application of minoxidil to areas such as the scalp for purposes for stimulating hair growth and prolonging the period of time that hair is in the anagen phase. Unfortunately, this method has been found to be effective in only a small proportion of users. Another known method for increasing hair diameter involves the application of silicone-containing treatments to areas such as the scalp. Disadvantageously, this method produces a "build-up" of silicone on the hair that tends to dull its physical appearance.
It would be desirable to provide a method of treating seborrhigic dermatitis and dandruff by improving these alternative manifestations indicative of an unhealthy scalp.